Re: [PATCH AUTOSEL 6.11 237/244] iomap: fix iomap_dio_zero() for fs bs > system page size

Sasha Levin
2024-10-06T00:30:24Z

On Wed, Sep 25, 2024 at 11:01:46PM +1000, Dave Chinner wrote:
>On Wed, Sep 25, 2024 at 07:27:38AM -0400, Sasha Levin wrote:
>> From: Pankaj Raghav <p.raghav@samsung.com>
>>
>> [ Upstream commit 10553a91652d995274da63fc317470f703765081 ]
>>
>> iomap_dio_zero() will pad a fs block with zeroes if the direct IO size
>> < fs block size. iomap_dio_zero() has an implicit assumption that fs block
>> size < page_size. This is true for most filesystems at the moment.
>>
>> If the block size > page size, this will send the contents of the page
>> next to zero page(as len > PAGE_SIZE) to the underlying block device,
>> causing FS corruption.
>>
>> iomap is a generic infrastructure and it should not make any assumptions
>> about the fs block size and the page size of the system.
>
>Please drop this. It is for support of new functionality that was
>just merged and has no relevance to older kernels. It is not a bug
>fix.
>
>And ....
>
>> +
>> + set_memory_ro((unsigned long)page_address(zero_page),
>> + 1U << IOMAP_ZERO_PAGE_ORDER);
>
>.... this will cause stable kernel regressions.
>
>It was removed later in the merge because it is unnecessary and
>causes boot failures on (at least) some Power architectures.

Dropped, and sorry about sending this one out twice!

--
Thanks,
Sasha